Working for the Oppressors: Lives of Others, 1984, Michael Clayton
Movies where the main character is working for the oppressors, the evil corporation...
in line with Lives of Others, 1984, Michael Clayton.
Some others similar: The Informant!, Serpico, Prince of the City.
I thought about The Insider, but the whistleblowing aspect begins at the start of the movie from the get go. I'd like watch movies where the protagonist anti-hero works for the 'wrong side' and undergoes a crisis of conscience.